Field of Invention
The present invention relates to detection probes and methods of use, and more particularly, stable free-radical probes (such as nitroxides) for use as contrast agents. The probes are optionally encapsulated in liposomes that are optionally targeted for specific binding sites on targeted tissue with a targeting ligand.
Description of the Related Art
Clinicians are concerned with detecting the presence of, and quantitatively measuring, a variety of substances via the use of many different analytical techniques. The most commonly used techniques employ absorbtiometry, both at visible and ultraviolet wavelengths; however, emission, flame photometry and radioactivity are also commonly used. Analyses based on the measurement of emitted light offer several distinct advantages over conventionally employed techniques, including high sensitivity, wide linear range, low cost per test, and relatively simple and inexpensive equipment.
The ability to label a specific cell type and image its presence, growth and/or movement in vivo, noninvasively and in real time would be of great importance in understanding the interactions of cells that regulate a spectrum of human physiology and in the diagnosis and evaluation of human diseases. Further, longer term imaging of tumor cells could, likewise, permit long-term studies of metastases.
In recent years, magnetic resonance imaging (MRI) with contrast media has been used to study a variety of important physiological processes. However, with the development of low-frequency electron paramagnetic resonance (EPR) spectrometers capable of detecting paramagnetic species in living animals in real time, EPR imaging is now an alternative technology that can, like MRI, address significant physiological questions. The challenge, however, has been the synthesis of paramagnetic spin probes that can provide these essential data and targeting of same to specific cells or aberrant tissue that is physiologically distinguishable from normal tissue.
It is, therefore, an object of the present invention to provide for a system for the detection of biological cells or tissues of interest, comprising a nitroxide or trityl stable free radical imaging probe that may optionally be encapsulated within a liposome, wherein the liposome may optionally be conjugated to targeting ligand specific to biological cells or tissues of interest.